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    <title>gl_Position - OpenGL ES 3.2 Reference Pages</title>
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    <div class="refentry" id="gl_Position">
      <div class="titlepage"/>
      <div class="refnamediv">
        <h2>Name</h2>
        <p>gl_Position — contains the position of the current vertex</p>
      </div>
      <div class="refsynopsisdiv">
        <h2>Declaration</h2>
        <p>
            <code class="varname">gl_Position</code> is a member of the
            <code class="varname">gl_PerVertex</code> named block:
</p>
        <pre class="programlisting">    out gl_PerVertex {
        highp vec4 gl_Position;
        highp float gl_PointSize;
    };</pre>
        <p>
        </p>
      </div>
      <div class="refsect1" id="description">
        <h2>Description</h2>
        <p>
            In the vertex, tessellation evaluation and geometry languages, a single
            global instance of the <code class="varname">gl_PerVertex</code> named block is available and
            its <code class="varname">gl_Position</code> member is an output that receives the
            homogeneous vertex position. It may be written at any time during shader execution.
            The value written to <code class="varname">gl_Position</code> will be used by primitive assembly,
            clipping, culling and other fixed functionality operations, if present, that operate on
            primitives after vertex processing has occurred.
        </p>
        <p>
            In the tessellation control language, the <code class="varname">gl_PerVertex</code> named block
            is used to construct an array, <code class="varname">gl_out[]</code>, whose <code class="varname">gl_Position</code>
            members hold the homogeneous control point position, which become available as inputs to the subsequent
            tessellation evaluation shader.
        </p>
        <p>
            The value of <code class="varname">gl_Position</code> (or the <code class="varname">gl_Position</code> member of the <code class="varname">gl_out[]</code>
            array, in the case of the tessellation control shader)
            is undefined after the vertex, tessellation control, and tessellation evaluation
            shading stages if the corresponding shader executable does
            not write to gl_Position. It is also undefined after the geometry processing stage if the geometry shader executable calls
            <a class="citerefentry" href="EmitVertex.xhtml"><span class="citerefentry"><span class="refentrytitle">EmitVertex</span></span></a> without having
            written <code class="varname">gl_Position</code> since the last call to <a class="citerefentry" href="EmitVertex.xhtml"><span class="citerefentry"><span class="refentrytitle">EmitVertex</span></span></a>
            (or hasn't written it at all).
        </p>
        <p>
            In the tessellation control, tessellation evaluation and geometry languages,
            the <code class="varname">gl_PerVertex</code> named block is used to construct an array, <code class="varname">gl_in[]</code>
            of per-vertex or per-control point inputs whose content represents the corresponding
            outputs written by the previous stage.
         </p>
      </div>
      <div class="refsect1" id="versions">
        <h2>Version Support</h2>
        <div class="informaltable">
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              <tr>
                <th style="text-align: left; border-right: 2px solid ; ">
                 
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; " colspan="4">
                <span class="bold"><strong>OpenGL ES Shading Language Version</strong></span>
            </th>
              </tr>
              <tr>
                <th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>Variable Name</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>1.00</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.00</strong></span>
            </th>
                <th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.10</strong></span>
            </th>
                <th style="text-align: center; border-bottom: 2px solid ; ">
                <span class="bold"><strong>3.20</strong></span>
            </th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td style="text-align: left; border-right: 2px solid ; ">gl_Position</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; border-right: 2px solid ; ">✔</td>
                <td style="text-align: center; ">✔</td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
      <div class="refsect1" id="seealso">
        <h2>See Also</h2>
        <p>
            <a class="citerefentry" href="gl_PointSize.xhtml"><span class="citerefentry"><span class="refentrytitle">gl_PointSize</span></span></a>
        </p>
      </div>
      <div class="refsect1" id="Copyright">
        <h2>Copyright</h2>
        <p>
            Copyright <span class="trademark"/>© 2011-2015 Khronos Group.
            This material may be distributed subject to the terms and conditions set forth in
            the Open Publication License, v 1.0, 8 June 1999.
            <a class="link" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
        </p>
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